Cloud liquid water path detectability and retrieval accuracy from airborne passive microwave observations over Arctic sea ice

Risse, Nils; Mech, Mario; Prigent, Catherine; Müller, Joshua J.; Crewell, Susanne

doi:10.5194/amt-19-2197-2026

Articles | Volume 19, issue 6

https://doi.org/10.5194/amt-19-2197-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Special issue:

HALO-(AC)³ – an airborne campaign to study air...

https://doi.org/10.5194/amt-19-2197-2026

© Author(s) 2026. This work is distributed under
the Creative Commons Attribution 4.0 License.

Articles | Volume 19, issue 6

Research article

|

01 Apr 2026

Research article |

| 01 Apr 2026

Cloud liquid water path detectability and retrieval accuracy from airborne passive microwave observations over Arctic sea ice

Nils Risse, Mario Mech, Catherine Prigent, Joshua J. Müller, and Susanne Crewell

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Final revised paper (published on 01 Apr 2026)
Preprint (discussion started on 11 Sep 2025)

Interactive discussion

Status: closed

RC1:
'Comment on egusphere-2025-3311', Christian Mätzler, 26 Sep 2025

Only some of my comments were taken into account.
For the rest, I miss a response of the authors.

Citation: https://doi.org/10.5194/egusphere-2025-3311-RC1
- EC1:
  'Editor comment', Andreas Richter, 27 Sep 2025
  
  Dear Christian Mätzler,
  Thank you for your comment. I think there is a misunderstanding about the publication process in AMT, which has two stages:
  1) A quick review, which basically gives the go-ahead for publication of the preprint. At this point, authors are not expected to implement larger changes in the document.
  2) The full review, which also allows for public comments and discussion. This is the current status of the manuscript. You are expected to provide your full review of the manuscript now, which should include those points you already made in the quick review and which have not yet been taken on by the authors.
  After this public discussion phase, the authors can submit a revised version of their manuscript, which will then be considered for publication, further revisions, or rejection.
  I hope this clarifies the procedure.
  Best regards,
  Andreas Richter
  
  Citation: https://doi.org/10.5194/egusphere-2025-3311-EC1
  - RC2: 'Reply on EC1', Christian Mätzler, 27 Sep 2025
    
    Dear Editor,
    Thank you for the explanations. I was not aware of this situation. Please let the authors know. I do not plan to do any further review of this rather complex work.
    Best wishes, Christian Mätzler
    
    Citation: https://doi.org/10.5194/egusphere-2025-3311-RC2
    
    AC2: 'Reply on RC4', Nils Risse, 13 Jan 2026
    
    The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3311/egusphere-2025-3311-AC2-supplement.pdf
    
    Citation: https://doi.org/10.5194/egusphere-2025-3311-AC2
RC3:
'Comment on egusphere-2025-3311', Anonymous Referee #2, 08 Oct 2025

See attached file

Citation: https://doi.org/10.5194/egusphere-2025-3311-RC3
- AC1: 'Reply on RC3', Nils Risse, 13 Jan 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3311/egusphere-2025-3311-AC1-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2025-3311-AC1
RC4:
'Comment on egusphere-2025-3311', Christian Mätzler, 11 Oct 2025

The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3311/egusphere-2025-3311-RC4-supplement.pdf

Citation: https://doi.org/10.5194/egusphere-2025-3311-RC4
- AC2: 'Reply on RC4', Nils Risse, 13 Jan 2026
  
  The comment was uploaded in the form of a supplement: https://egusphere.copernicus.org/preprints/2025/egusphere-2025-3311/egusphere-2025-3311-AC2-supplement.pdf
  
  Citation: https://doi.org/10.5194/egusphere-2025-3311-AC2

Peer review completion

AR – Author's response | RR – Referee report | ED – Editor decision | EF – Editorial file upload

AR by Nils Risse on behalf of the Authors (13 Jan 2026) Author's response Author's tracked changes Manuscript

ED: Referee Nomination & Report Request started (16 Jan 2026) by Andreas Richter

RR by Anonymous Referee #2 (26 Jan 2026)

Suggestions for revision or reasons for rejection

The discussion in Sec 4.1 regarding the mis-match between the observed and retrieved brightness temperatures in clear-sky cases is still not satisfactory. The large tail of positive observation-simulation differences at 118 and 183 GHz is not fully explained, and related analysis is only in the author response and not included in the revised text. Although fig Rev1 in the author response shows that the agreement in the central arctic region is generally good, there are still a large number of significant differences which do not correspond to thin sea ice as detected by VELOX. Perhaps I could infer from the later discussion in Sec 4.2. that this could be caused by thin ice which VELOX misses, but I would prefer it if the authors discussed this properly in Sec 4.1.1. I do not think that Fig Rev1 is consistent with the L323: "These cases occur mainly over young sea ice as identified from VELOX...". However, the figure is not included in the revised text so the reader is not able to draw their own conclusions about the validity of this statement and may get a misleading impression.

The sensitivity of the retrieval to the a-priori CLWP, as shown by figure Rev4 in the response, is a significant result, but is only very briefly discussed in the revised text and the results are not shown. It is a further indication that the CLWP is not strongly constrained by the retrieval, presumably due to the ambiguity with the other parameters. For me, a key conclusion of this paper is that to accurately retrieve CLWP from passive microwave observations over sea ice, it is necessary to provide stronger a-priori constraints on the surface parameters.

L376: I still think this is too positive a statement regarding the performance of a retrieval with such significant biases. Perhaps replace "the retrieval approximates the true CLWP" with "the retrieved CLWP is correlated with the true CLWP".

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ED: Publish subject to minor revisions (review by editor) (11 Feb 2026) by Andreas Richter

AR by Nils Risse on behalf of the Authors (03 Mar 2026) Author's response Author's tracked changes Manuscript

ED: Publish as is (13 Mar 2026) by Andreas Richter

AR by Nils Risse on behalf of the Authors (22 Mar 2026) Manuscript

Short summary

Clouds play a crucial role in the Arctic climate system, particularly cloud liquid water droplets. However, there is currently a measurement gap for cloud liquid water over sea ice. We present a method to estimate cloud liquid water over Arctic sea ice using airborne passive microwave observations from the HALO-(𝒜𝒞)³ campaign. Evaluation with other airborne sensors highlights both the limitations and potential of the retrieval. This approach is promising for future applications to satellites.